*Groups from the 8th Air Force.
+Groups still training in the U.S. in late 1942.

The 12th Air Force was activated on August 20, 1942 with the organization shown above.
General H. H. "Hap" Arnold and US Chief of Staff, General George C. Marshall chose Brigadier General
Jimmy Doolittle as head of the 12th Air Force and Doolittle formally assumed command in the
UK on September 23, 1942. The B-25s of the 310th Bombardment Group were the first planes in
the 12th AF to arrive in Europe during October, 1942. They flew over by way of Maine, Labrador,
Greenland, Iceland and Prestwick, Scotland. The 310th BG B-25s were followed by A-20 Havocs
from the 47th BG and B-26 Marauders of the 319th BG but winter weather interfered with this
route and subsequent groups took the southern route via Florida; Boringuen Field, Puerto Rico;
Waller Field, Trinidad; Atkinson Field, British New Guiana (Guyana); Belem and Natal, Brazil;
Ascension Island; Dakar, Marrakech, Telergma, and some other North African destinations.
The largest air force ever assembled at that time, the 12th AF was
initially assigned some 70,000 men and 1400 planes for the invasion of Vichy French held
North Africa (Operation Torch) on November 8, 1942. In November 1942, on order of General
Dwight D. Eisenhower, Gen. Carl Spaatz reorganized the Allied Air Forces in North Africa.
Spaatz became commander of the allied Northwest African Air Forces (NAAF) in February 1943.
By March 1943 he took command of the Twelfth Air Force in North Africa as a temporary lieutenant
general. Doolittle, who was promoted to Major General in November 1942, took over command of the
Northwest African Strategic Air Force (NASAF) in March, 1943. Air Vice Marshall Sir Arthur Coningham became
commander of the Northwest African Tactical Air Force (NATAF).

At the Casablanca Conference in January of 1943, British Prime Minister Winston Churchill
and United States President Franklin Roosevelt reorganized the Mediterranean air forces naming Air Chief
Marshal Sir Arthur W. Tedder as Air Commander-in-Chief of the new Mediterranean Air Command (Allied). Both British and American officers became part of
the new command structure with the intent of forcing international cooperation.
According to "Craven and Cate, Eds., The Army Air Forces in WWII, Vol. 2," this was the new organization as of February 17, 1943:

Mediterranean Air Command (Allied)Air Chief Marshal Sir Arthur Tedder

RAF Middle East CommandAir Chief Marshal Sir Sholto Douglas

RAF Air Headquarters, MaltaAir Vice-Marshal Sir Keith Park

Northwest African Air ForcesLieutenant General Carl Spaatz

The structure of the Northwest African Air Forces (NAAF) was based on an air interdiction model
pioneered and developed by Tedder and Air Vice-Marshal Arthur Coningham during the successful RAF
campaigns in Egypt and Libya. During this time, the RAF coordinated three main combat forces: 1) A long range bomber force (No. 205 Group);
2) A marine anti-shipping force (No. 201 Group); and 3) a close air support tactical force (Air Headquarters, Western Desert).
Consequently, the three main combat commands of NAAF consisted of:

A key feature of the reorganization was close cooperation between British RAF and American USAAF commanders.
Each unit with a commander from one air force was assigned a deputy commander from the other air force. In keeping
with this policy, Spaatz's Deputy Air Commander was Air Vice-Marshal James M. Robb who handled NAAF operations. Furthermore,
the new Mediterranean Air Command organization and other implementations made by Churchill, Roosevelt, and their staffs
at the Casablanca Conference, were intended to foster parity between the naval, air, and ground forces. Rapid and efficicient
tactical support of ground operations was especially important. The MAC triforce model was practiced throughout WWII and today is still the
classic model for interdictory operations in the USAF.

Within the official Mediterranean Air Command organizational structure, the 12th Air Force did not legally exist
from February 18 through most of 1943. This unusual state of affairs caused great concern among many
USAAF officers including Spaatz and Doolittle. Upon inquiring with Eisenhower about the matter, Spaatz was
informed that he would assume command of the 12th Air Force for administrative purposes only on March 1, 1943.
At that time, Spaatz was already the commander of the Northwest African Air Forces (NAAF), the official Allied
organization that had absorbed all of the 12th Air Force's groups and administrative personnel. The overall effect
was that the 12th Air Force ceased to exist for most of 1943. In fact, the only mention of the 12th among the major
commands of NAAF was the XII Air Support Command, a subordinate command of
Coningham's NATAF. Because Spaatz was involved primarily with higher level organizational and political planning,
the daily operations of NAAF were mainly the responsibility of his deputy, so it was Robb who handled operations
of the 12th AF groups. Of course the 12th Air Force still existed in the USAAF and in 1943 it was still the largest air force
ever assembled, despite its non-existence within the official Allied organization of the Mediterranean
Air Command.

The organization of the 12th AF is shown above at the time of Operation Husky
or the invasion of Sicily on July 10, 1943. One month prior to Operation Husky was the invasion of Pantelleria or
Operation Corkscrew. For ten days 12th AF bombers pounded the island of Pantelleria
using 1100 planes and 1571 tons of bombs during one four-day period causing the Italians
to surrender immediately when British forces landed on June 11, 1943. This is believed to be the first time ground troops surrendered due to
air power alone. The Italian garrisons on the islands of Linosa and Lampedusa surrendered soon after, clearing the way for the Sicilian (Operation Husky) and mainland Italy Campaigns.

Here is an excellent Air Force link describing the history of this period.

In November of 1943 the 15th Air Force was created. The four B-17 groups, the
two B-24 groups, and the three B-26 groups of the 12th Air Force were transferred
to the 15th Air Force along with the three P-38 groups, the 325th FG which had
just converted to P-47s, and the 68th Recon Group. The three B-26 groups transferred
back to the 12th Air Force in January 1944. In November of 1943, General Jimmie Doolittle
was named Commander of the 15th Air Force which became the strategic air force in the MTO
while the 12th Air Force became the tactical air force in the MTO. From January 1944 to
September 1945 Doolittle commanded the 8th Air Force in Europe and the Pacific, until the end of the war.
Doolittle was promoted to lieutenant general on March 13, 1944. By January 1944, Carl Spaatz
commanded all of the U.S. Strategic Air Forces in Europe including the Eighth Air Force under Doolittle
in England, and the Fifteenth Air Force under General Nathan Twining in Italy. Below is shown the
organization of the new 12th Tactical Air Force as of January 1, 1944. At that time, Major General
John K. Cannon was named CO of the 12th Air Force and the Mediterranean Allied Tactical Air Force (MATAF).

The above 12th Air Force organizational information is taken from the USAAF Film"The 12th Air Force Story."